1. Field of the Invention
The present invention relates to a method and apparatus for writing data into disk storages in an array disk storage system. The method and apparatus according to the present invention are applicable to an array disk storage system, a multi-volume data storing system, and the like, for processing data by a computer.
2. Description of the Related Arts
In general, in an array disk storage system having an array of disk storages, a plurality of regular disk storages, e.g., eight disk storages, and a disk storage for parity data are provided. Data writing and data reading are carried out to and from the regular disk storages, and the parity data generated from the data to be written to the regular disk storages is written to the disk storage for parity data. Therefore, if one of the disk storages becomes faulty, the data can be restored from the remaining functioning disk storages, and accordingly, the operation of reliability of the system is ensured.
In the array disk system, when a number equal to or more than a predetermined number of faults in the disk storages are detected, the detected faulty disk storage is excluded, a spare disk storage is used as a replacement for the excluded faulty disk storage, and the restored data generated from the remaining functioning disk storages is written to the spare disk storage.
After the faulty disk storage is repaired and brought back to the functioning state, or is replaced by a fresh disk storage as a new disk storage, the data stored in the spare disk storage is written, i.e., copied, to the new disk storage, to restored a normal operating state.
In this case, if the copying of the restored data from the spare disk storage to the new disk storage is interrupted, and a new data is written to a portion of the region of the spare disk storage from which a writing of restored data to the new disk storage has been completed in accordance with a write instruction from an upper grade device, this operation becomes complex and disadvantageous in that the data of the disk storages in the data restoring operation must be changed, and that a separate copying of the data in the above-mentioned portion of the region of the spare disk storage, and a storage of the address of this portion of the region, become necessary.
Also, if new data is written to a portion of the region of the new disk storage to which the copying, of the restored data from the spare disk storage is to be carried out, the process becomes complex and disadvantageous in that the new data written to the above-mentioned portion of the region must be saved, to prevent the destruction of the written new data by the subsequent writing of the restored data, or a subsequent writing of the restored data must be prohibited.